5 Ways to Tell Spring Has Arrived
National Wildlife Federation Conservation Hall of Fame honoree Henry David Thoreau wrote in his journal on March 17, 1857, “No mortal is alert enough to be present at the first dawn of spring.” How right he was, given that the arrival of spring is not quite as perfectly defined as you might think.
The timing of spring in your region depends on a number of things, including local climate and where you live (spring and autumn switch time of year north and south of the equator).
Here are five ways to tell if spring is here where you live.
Astronomically: Spring begins at the March equinox in the northern hemisphere and at the September equinox in the southern. The equinox marks the date on which night and day are of equal length (12 hours) and is caused by the tilting of the northern hemisphere toward the sun as the planet speeds through its annual orbit. In northern temperate zones, the spring equinox occurs between March 19 and 23, changing from year to year because the tilt of the Earth and its relationship to the sun varies. Nevertheless, using the equinox to mark spring is a clear, objective way to say spring is here, independent of local variations.
Among Swedish meteorologists, spring is defined as occurring when the average daytime temperature lies above freezing for seven consecutive days, meaning that in Sweden, spring arrives at different times at different latitudes.
U.S. meteorologists may define spring as the period of transition from winter (defined as the three coldest months) to summer (the three hottest months), which means that meteorological spring generally runs from March1 to May 31, subject to climate variations.
Another definition of spring could be called the no-sno method, in which spring in a given area begins on the day when precipitation is likely to be rain rather than snow.
In some areas and cultures, the start of spring is marked by the blooming of certain plants or the appearance of certain animals, factors that are changing in the wake of global warming, indicating that spring is coming earlier in some areas. A spring arrival timed by the behavior of living things, to say nothing of the thawing of snow and frost, is bound to vary from year to year, affected as it is likely to be in some areas by factors such as El Niño and El Niña ocean currents, which bring warming and cooling trends respectively.
We think of spring as a time or rebirth and the promise of relief from cold, but it has its dark side. It is the season in which air masses cold from winter meet air masses warming from increased sunlight, which can result in tornadoes and violent thunderstorms. Spring in many areas is also a time of floods.
No matter. For most of us in temperate zones, spring is a time to revive and get outside. Thoreau again, in Chapter 17 of his book Walden: “One attraction in coming to the woods to live was that I should have leisure and opportunity to see the Spring come in.” Seasons may come and go, but our pleasure in greeting spring remains unchanged across the years.